With the exception of bio-diesel, ethanol, direct hydrogen ICE and ICE hybrid engines, the focus on commercialized and near-term alternative power choices are nearly all electric powered, whether by hydrogen fuel cells or new energy storage technologies. Below is a brief look at each of today's major players.
Hydrogen Fuel Cells
The commercial application of hydrogen fuel cells in lift trucks is currently taking place at several sites. Unlike a battery, which must be recharged after use, a fuel cell produces electric current continuously, provided there is a constant supply of hydrogen fuel and oxygen. A short refueling time of only minutes makes a hydrogen fuel cell-powered fleet ideal for multi-shift, constantly running operations.
While fuel cells are the most widely commercialized energy source among the emerging technologies, there are some points to consider before converting a fleet to hydrogen. Hydrogen fuel cells are becoming more efficient and are 100% green at the point of use. However, in the total environmental model and calculation, it is necessary to factor in where the hydrogen originated from, the economic and environmental cost of distribution, and the overall carbon footprint.
Advantages
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Zero emissions at the point of use
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Very fast refueling time
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Potential for increased productivity
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Reduced battery inventory
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Potential to eliminate battery change equipment, space and personnel
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Voltage and truck performance remain stable over a shift
Disadvantages
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Up-front capital investments, in both on-truck and infrastructure costs
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Hydrogen fuel delivery is not readily available in all areas; delivery infrastructure is not mature
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Currently produced from fossil fuels in many cases (Commercial bulk hydrogen, for example, is usually produced by the steam reforming of natural gas.).
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Fuel cell packs are not yet available for all lift truck types, making full fleet deployment more difficult
Lithium-Ion Batteries
The most promising family of battery chemistries, in terms of improving recharge times and high energy density, is lithium ion. There are two general approaches to lithium-ion batteries: a large format approach and a smaller cell approach. The larger format approach typically includes advanced nano-based materials for improved performance and safety. The smaller cell approach combines large quantities of commodity cells using conventional chemistries but relies on sophisticated electronics to ensure safety.
While the larger format nano-based chemistries promise superior charge times, they are more expensive and further out on the development horizon. Both approaches to lithium ion cost multiples more than lead acid batteries, but longer life and zero maintenance offer the possibility of favorable total lifecycle costs.
Companies are taking a hard look at the economies involved with lithium ion and advanced battery technology. Based on advancements in other industries, it is expected that lithium ion and other advanced battery technologies will get serious play in the material handling space in the future.
Advantages
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Short recharge time
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Higher energy density (especially advantageous for Class II applications)
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Higher energy efficiency and reduced carbon footprint
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Suited to smaller fleets and a wider range of applications and truck types
Disadvantages
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High initial cost
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Significantly lighter weight affects need for lift truck counterbalance weight
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Early stage commercialization for motive power
Advanced Lead-Acid Technologies
Much research and development is focused on improving current wet cell lead-acid battery technologies. New advances include thin-plate pure lead, carbon lead and carbon-graphite foam grid technology. These batteries, with potentially shorter lead times to full commercial use in lift trucks, share the advantages of being based on existing technology.
With a size and weight comparable to normal lead-acid batteries, advanced lead-acid batteries could be used as drop-in replacements in existing electric lift trucks and should not require substantial investments in additional infrastructure or charging setups.
Advantages
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Short charging time
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Greater cycle life
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Standard dimensions, plug-and-play alternative to lead-acid batteries
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Lower cost than lithium-ion alternatives
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Shares high rate of recycling potential with existing lead-acid batteries
Disadvantages
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New technology, only now moving into motive power
Battery Hybrids
As in the auto industry, the battery to be used in combination with the ICE will likely be either nickel metal-hydride (Ni-MH) or lithium ion (Li-Ion). Compared to an ICE truck, a battery/ICE hybrid will reduce fuel consumption and engine emissions, possibly eliminating emissions during idling. These benefits will likely come at an increase in initial truck costs, which would need to be factored into the overall lifecycle cost analysis.
Considering that fully electric lift trucks are already prevalent in the market with many potential improvements in battery technology on the horizon, the benefits of battery/ICE hybrids will be limited to traditional ICE truck segments, in which they may soon compete with fully electric lift trucks.
Advantages
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Reduced energy consumption compared with ICE
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Reduced emissions compared with ICE
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Quick refuel, duty cycle similar to ICE
Disadvantages
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Higher initial cost, still likely to depend on lithium ion
Sources: Darel Reed, manager of technology development, NACCO Materials Handling Group, and Patrick Duhaime, vice president of marketing, Hyster Co.
